This invention relates to a continuous emulsifying apparatus disposed in an oil supply line which forms a main unit of a system which produces emulsified fuel oil for combustion purposes.
Conventionally, there has been proposed several apparatuses for mixing at least two different kinds of liquids in the line. One of such apparatuses utilizes propeller-shaped agitator blades which rotate in a casing. However, the apparatus has not been commercially put into practice in the emulsification of fuel oil and water which have no affinity for each other, since the apparatus has the following defects.
(1) insufficient mechanical energy,
(2) insufficient emulsification due to the short path.
For facilitating the understanding of the present invention, the difference between the mixing and the emulsifying is explained hereinafter.
In case at least two different kinds of liquids which have no affinity for each other are brought together to produce one liquid, the produced liquid which is the mixture of two liquids can have a uniform nature as time passes by. This phenomenon is called "mixing". The mechanical agitation is one of the means to shorten the time necessary for such mixing. The conventional mixing apparatus is used for such mechanical agitation.
However, when the two different kinds of liquids have no affinity for each other, they maintain the mixture condition so long as the agitation is continued but readily separate from each other as soon as the agitation is ceased.
In this case, when the agitation which is applied to the liquids as a mechanical force is greatly increased, the liquids are subjected to a shearing force, wherein one liquid is dispersed in the other liquid in the form of fine droplets thus providing a milky fluid, an emulsion and such state of emulsion continues for a certain period. The emulsion period becomes prolonged as the diameter of the fine droplets becomes smaller.
An emulsion which can maintain such prolonged emulsion period is referred to as "an emulsion having high stability".
In the combustion of emulsified liquid oil, an especially high emulsion is required, since the separation of the mixture or the emulsion into the respective liquids results in unstable combustion and in a worst case leads to shut off of the combustion.
Accordingly, it is an object of the present invention to provide a continuous emulsifying apparatus which can produce a highly-stable emulisified liquid by applying a sufficient mechanical force such as a high shearing force or impact force to the liquids to be emulsified in such a manner that the liquids are repeatedly forced to pass through a desired number of minute gaps defined between stators and rotors while preserving "the restriction of the increase of flow resistance" which is a prerequisite for mixing apparatuses in general.
The apparatus of this invention comprises a casing having at least two inlets for different kinds of liquids in one end thereof and an emulsified liquid outlet at other end thereof, a plurality of circumferential ribs formed on the inner wall of the casing in a spaced-apart manner in a longitudinal direction, a plurality of radially equidistant protrusions formed on the inner surface of the casing, each protrusion extending in a longitudinal direction and having the same inner diameter as those of the circumferential ribs, the protrusions crossing the circumferential ribs, thus providing a plurality of slits in the inner wall of the casing, and an impeller rotatably and concentrically disposed in the casing, the impeller consisting of a rotating shaft and a desired number of rows of radially-equidistant agitator blades mounted on the shaft, the agitator blades having an outer diameter slightly smaller than an inner diameter of the circumferential ribs thus providing the minute gaps between the blades and the ribs.
Due to the above construction, the liquids are alternately subject to the slits which try to stop the flow of liquids and the impeller which rotates at a high speed. This implies that the liquids are repeatedly forced to pass through the minute gaps provided between the protrusions of the stationary slits and the outer circular periphery of the impeller. During the above flow of the liquids passing through the gaps, the liquids are subject to mechanical force such as shearing and impact, whereby a highly stable emulsion is obtained.